Parasitic angiosperms are represented in the majority of ecosystems worldwide and are considered keystone species in many ecosystems worldwide. Parasitic plants affect population dynamics, community structure and plant diversity through (1) direct ‘parasite effects’ on the host community and (2) indirect ‘litter effects’ through the redistribution of nutrients in the ecosystem. (1) Hemiparasitic infection directly reduces host and total aboveground biomass production. If a host preference exists for dominant graminoids, hemiparasitic infection can alter the competitive balance in favour of forbs. This reduced competition may in turn increase species richness and accelerate the restoration of species-rich grasslands. (2) Most parasites shed their leaves or die of early in the season and produce high quality litter that mineralizes faster. This can enhance nutrient cycling and could indirectly reduce species richness when higher nutrient availability favours competitive species.
Here we focus on the indirect effect of litter of two hemiparasitic plants (Rhinanthus angustifolius and Pedicularis sylvatica) on the composition of their host communities. In a tracer experiment we determined which co-occurring species profit most of the addition of hemiparasitic litter labelled with nitrogen-15 (15N). We found tenfold differences between species. For Rhinanthus litter, we found a significant positive relation between the N derived from the applied litter (Ndfl) and specific leaf area (SLA). We suggest that plants with a higher SLA have less root biomass (and thus less N storage), but a higher N uptake rate. Because of N stored in root biomass, plants with a lower SLA would take up relatively less N from the soil (and the added litter). Legume species have relatively low Ndfl values, which is due to biological N fixation from the air. On the other hand, saplings and dwarf shrubs have relatively high Ndfl values.

@inproceedings{4361640,
abstract = {Parasitic angiosperms are represented in the majority of ecosystems worldwide and are considered keystone species in many ecosystems worldwide. Parasitic plants affect population dynamics, community structure and plant diversity through (1) direct {\textquoteleft}parasite effects{\textquoteright} on the host community and (2) indirect {\textquoteleft}litter effects{\textquoteright} through the redistribution of nutrients in the ecosystem. (1) Hemiparasitic infection directly reduces host and total aboveground biomass production. If a host preference exists for dominant graminoids, hemiparasitic infection can alter the competitive balance in favour of forbs. This reduced competition may in turn increase species richness and accelerate the restoration of species-rich grasslands. (2) Most parasites shed their leaves or die of early in the season and produce high quality litter that mineralizes faster. This can enhance nutrient cycling and could indirectly reduce species richness when higher nutrient availability favours competitive species.
Here we focus on the indirect effect of litter of two hemiparasitic plants (Rhinanthus angustifolius and Pedicularis sylvatica) on the composition of their host communities. In a tracer experiment we determined which co-occurring species profit most of the addition of hemiparasitic litter labelled with nitrogen-15 (15N). We found tenfold differences between species. For Rhinanthus litter, we found a significant positive relation between the N derived from the applied litter (Ndfl) and specific leaf area (SLA). We suggest that plants with a higher SLA have less root biomass (and thus less N storage), but a higher N uptake rate. Because of N stored in root biomass, plants with a lower SLA would take up relatively less N from the soil (and the added litter). Legume species have relatively low Ndfl values, which is due to biological N fixation from the air. On the other hand, saplings and dwarf shrubs have relatively high Ndfl values.},
author = {Demey, Andreas and Staelens, Jeroen and Baeten, Lander and Boeckx, Pascal and Hermy, Martin and Verheyen, Kris},
booktitle = {Applications of Stable Isotope Techniques to Ecological Studies, 8th International conference, Abstracts},
language = {eng},
location = {Brest, France},
title = {Nutrient input from hemiparasitic litter favors species with a high-nutrient strategy},
year = {2012},
}